1. Field of the Invention
The present invention relates to a lens apparatus for use in a video camera lens, a video camera, a television camera lens or a television camera, and to an image-taking apparatus having the lens apparatus and a photoelectric conversion element which photoelectrically converts a subject image formed by the lens apparatus.
2. Description of the Prior Art
In recent years, in a zoom lens for use in a broadcast television camera such as an ENG camera, a zoom track function provided for a zooming control accessory mountable on the zoom lens has allowed setting a limit value on the drive range of the zoom lens. An operation example of the zoom track function of this type is described below with reference to FIGS. 9 to 13.
FIGS. 9 to 13 are schematic diagrams and block diagrams showing the appearance of an ENG lens which supports the conventional zoom track function (for example, see Japanese Patent Application Laid-Open No. 2000-284164). In FIGS. 9 to 13, reference numeral 1 shows a zoom lens for use in a broadcast television camera such as an ENG camera, 2 a lens barrel, 3 a drive unit, 4 a focus ring, 5 a zoom ring, 6 an iris ring, 7 an extender lever, 8 a zoom preset speed mode switch lever, 9 a frame preset switch, 10 a memory switch, 11 a send-back switch, 12 a zoom operation switch, 13 an iris operation change switch, 14 an iris momentary auto-switch, 15 a focus speed adjustment trimmer, 16 an iris gain adjustment trimmer, 17 a zoom mode adjustment trimmer, 18 a focus servo/manual switch knob, 19 and 20 zoom remote and focus remote 20-pin connectors, 21 a zoom remote 8-pin connector, 22 a zoom speed adjustment volume, 23 a zoom servo/manual switch knob, 24 a macro-button, 25 a shuttle shot switch, 26 a DIP switch unit, 27 a VTR switch, 28 a DIP switch I, 29 a DIP switch II, 30 a DIP switch III, 31 a DIP switch IV, 32 a DIP switch V, 33 a DIP switch VI, 34 a DIP switch VII, 35 a DIP switch VIII, 36 a zoom operation control accessory, 37 a 20-pin connector, 38 a zoom remote operation switch, 39 a zoom track telephoto position adjustment remote volume, 40 a zoom track wide-angle position adjustment remote volume, 41 a zoom track function valid/invalid remote switch, and 42 a zoom track valid indicator.
Although the internal structure of the lens barrel 2 is not shown, the lens barrel 2 has, in order from an object side, a fixed focus lens, a movable focus lens, a zoom lens, an iris, a relay lens and the like provided therein, and an extender is disposed behind them. The focus ring 4 is rotated around an optical axis to move the movable focus lens forward and backward in the optical axis direction to achieve focusing. The zoom ring 5 is rotated around the optical axis to move the zoom lens forward and backward in the optical axis direction to achieve zooming.
The iris ring 6 is rotated around the optical axis to adjust the diaphragm diameter of the iris. The drive unit 3 is mounted on a side portion of the lens barrel 2. The drive unit 3 has a focus drive motor, not shown, arranged therein. The drive force of the focus drive motor is transmitted to the focus ring 4 through a transmission mechanism, not shown, to drive the focus ring 4 for rotation around the optical axis. Alternatively, the focus ring 4 may be rotated manually without mounting the focus drive motor on the drive unit 3, by way of example.
The drive unit 3 has a zoom drive motor arranged therein. The drive force of the zoom drive motor is transmitted to the zoom ring 5 through a transmission mechanism, not shown, to drive the zoom ring 5 for rotation about the optical axis.
Similarly, the drive unit 3 has an iris drive motor, not shown, arranged therein. The drive force of the iris drive motor is transmitted to the iris ring 6 through a transmission mechanism, not shown, to drive the iris ring 6 around the optical axis.
The zoom operation switch 12 is formed on the drive unit 3. The zoom operation switch 12 is pressed to a telephoto side or a wide-angle side to drive the zoom ring 5, thereby moving the zoom lens toward the telephoto side or wide-angle side.
A zoom drive speed can be adjusted in accordance with the amount of pressing (the operation amount) of the zoom operation switch 12. As the pressing amount is larger, the zoom drive speed is higher. The frame preset switch 9 can be pressed to move the zoom lens to a previously stored zoom position. The zoom drive speed in this case can be changed by operating the speed mode switch lever 8. Specifically, the zoom drive speed can be changed to one of the highest possible speed or a preset speed.
The send-back switch 11 can be turned on to display return video on a viewfinder. The iris operation switch 13 can be flipped to switch between manual and servo operations of the iris.
While the iris auto-switch 14 is ON, the iris operation is switched to a servo operation. The set zoom position or the zoom drive speed are set by simultaneously operating the memory switch 112 and the shuttle shot switch 25, the frame preset switch 9 or the zoom operation switch 12. A zoom or focus operation control accessory (20-pin) is connected to the zoom remote and focus remote 20-pin connectors 19 and 20.
The focus servo/manual switch knob 18 can be flipped to switch between manual and servo operations of the focus. A zoom operation control accessory (8-pin) is connected to the zoom remote 8-pin connector 21. The zoom speed adjustment volume 22 adjusts the speed over the entire zoom range when a zoom operation is performed by the zoom operation switch 12. The zoom servo/manual switch knob 23 can be flipped to switch between manual and servo operations of the zoom. The macro-button 24 is used when a user intends to take a closeup of a subject located closer than the closest focusing distance. A built-in extender is operated by manipulating the extender lever 7. A focus speed is adjusted by the focus speed adjustment trimmer 15. An iris servo gain is adjusted by the iris gain adjustment trimmer 16. The zoom mode adjustment trimmer 17 is used to adjust a change caused by the zoom speed adjustment volume 22. The zoom lens is moved forward and backward at the highest speed to zoom positions which are stored corresponding to ON/OFF of the shuttle switch 25. The DIP switches 28 to 34 are used to perform various setting such as a function assignment to the VTR switch 27 and the like. The DIP switch 35 is not assigned any setting item. The VTR switch 27 is used to perform a start operation or a stop operation of a VTR. The zoom remote operation switch 38 is disposed swingably with a neutral position as a reference. When the zoom remote operation switch 38 is pressed to the telephoto side or wide-angle side, the zoom ring 5 is rotated to the telephoto side or wide-angle side. A zoom drive speed can be adjusted by the amount of pressing (the operation amount) of the zoom remote operation switch 38. As the pressing amount is larger, the zoom speed is higher. The zoom operation control accessory 36 is connected to the zoom remote and focus remote 20-pin connectors 19 and 20 through the 20-pin connector 37 of the zoom operation control accessory 36. The zoom track telephoto position is adjusted by operating the zoom track telephoto position adjustment remote volume 39 of the zoom operation control accessory 36, and the zoom track wide-angle position is adjusted by operating the zoom track wide-angle position adjustment remote volume 40. As a result, the drive range of the zoom lens can be set. The zoom track function can be switched between valid and invalid states by operating the zoom track function valid/invalid remote switch 41 of the zoom operation control accessory 36. In addition, the valid or invalid state of the zoom track function can be checked through the zoom track valid indicator 42 mounted on the zoom operation control accessory 36.
The aforementioned conventional example, however, has the following disadvantages since the drive unit alone cannot set the zoom track position.
Specifically, since the zoom operation control accessory (20-pin) is necessary to use the zoom track function, the zoom lens on which the accessory is mounted has poor portability. Especially when a user shoulders the lens to take images for news and the like without using a tripod, the user has great difficulty in using the zoom track function. Also, the drive unit has a number of the operation switches thereon as described above, and it is extremely difficult to newly provide a zoom track position adjustment volume and a zoom track function switch in limited space on the drive unit. In addition, erasing the stored zoom track position requires another memory operation by setting the telephoto end or wide-angle end as a zoom track position, involving significant effort. Moreover, the valid or invalid state of the zoom track function can be checked only through the zoom track valid indicator mounted on the zoom operation control accessory (20-pin), and if the zoom track function is realized by the drive unit alone, no means for checking is provided.
It is a first object of the present invention to allow realization of a zoom track function by a drive unit alone without newly adding an operation switch and with a minimum required amount of operation.
It is a second object of the present invention to separately enable erasure of stored contents of zoom track positions and switch between valid and invalid states of the zoom track function only with an operation switch on the drive unit and through a minimum required amount of operation.
It is a third object of the present invention to allow visual recognition of switch between valid and invalid states of the zoom track function without newly mounting an indicator on the drive unit.